Total joint arthroplasty is an effective treatment for relieving pain and restoring function for patients with diseased or damaged joints. Hundreds of thousands of total joint replacements are implanted each year in the United States alone, and these numbers will increase as the population continues to age and as the indications for joint arthroplasty extend to younger patients. Despite this clinical success, many patients require painful and costly revision surgery because their joint replacements loosen secondary to implant wear and the associated osteolysis. Wear of the surfaces of the man-made materials that form the joint implant is now recognized as the major obstacle to long-term success and has been the focus of considerable research aimed at understanding the clinical, biological, engineering and materials factors that influence the wear process. Research questions based on these factors formed the agenda of a 1995 NIH/AAOS workshop attended by clinicians, biologists, engineers, and materials scientists studying the wear problem. In the ensuing few years, clinical concern has grown, but fortunately has been accompanied by important advances in understanding the clinical impact of the problem, the biological reaction to wear debris, and design and material factors that control mechanics of wear. Given these discoveries, a follow-up workshop is proposed with the goals of: defining the current research knowledge base on the wear problem; addressing intervention and prevention strategies involving biological, biomechanical, and biomaterials solutions; attracting new investigators to research the wear issue; and drafting a proceedings for rapid and widespread dissemination of workshop findings on the internet. The emphasis will be on reviewing what is known about implant wear, defining what important aspects remain unknown, and identifying future research directions.